Scientists Just Discovered the Roundest Object in the Known Universe

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Geometry
is everywhere
in nature - we see sixfold symmetry in snowflakes, fractal patterns in
broccoli, and Fibonacci spirals in red cabbage. But a perfectly formed sphere?
That’s a whole lot harder to find.

While
all those moons, stars, and planets out in space appear to be pretty round, the
reality is they’re getting flattened, squished, and skewed with every rotation
on their axis. But scientists have managed to find a star so round, it’s the
most spherical object in the known Universe.

The
star in question is called Kepler 11145123 (or KIC 11145123), located some
5,000 light-years from Earth. When a team led by astronomer Laurent Gizon
from Max Planck Institute for Solar System Research and the University of
Göttingen in Germany first discovered it, they used a technique called asteroseismology to
determine how spherical it is.

Strangely
enough, this slowly rotating gas sphere hasn’t been flattened as it spins on
its axis - its roundness is so beautifully intact, the researchers say it’s the
most spherical natural object known to science.

"[K]epler
11145123 the roundest natural object ever measured, even more round than the
Sun," says
Gizon.

The
discovery has opened up a whole bunch of questions - mainly how on Earth did
this thing get so round - but let’s run through what we do know about nature’s
most spherical object. The technique of asteroseismology allows researchers to
calculate the oscillation of stars, and use that to figure out its oblateness -
basically how much flattening or compression a circle or sphere has.

When
stars, planets, and moons spin on their axis, they experience centrifugal
forces, which pull their equatorial regions away from the centre of rotation.
This causes these round objects to end up slightly more wide than they are tall
- or 'oblate'.

The
faster a cosmic body spins, the more oblate it becomes, but KIC 11145123 is a
particularly slow spinner. The researchers calculate that it spins three times
more slowly than our Sun, but is more than twice the size.

In
terms of exact measurements of 'roundness', they calculated that the difference
between the equatorial and polar radii of the star is only 3 km - "a
number that is astonishing small compared to the star's mean radius of 1.5
million km; which means that the gas sphere is astonishingly round", they
report.

To
put those numbers into perspective, our Sun has a radius at the equator that is
10 km larger than at the poles, and for our lumpy old Earth, this difference is
21 km. But things don’t really add up, because the team says KIC 11145123 is
even less flattened than implied by its slow rotation rate. As
Michael Byrne explains for Motherboard, asteroseismology is based on our
ability to separate out the frequencies of acoustic waves emanating from a
star's interior.

"Using
these waves to visualize the guts of the star, they found that KIC 11145123's
exterior layers are rotating faster than its core, this is what is likely
causing the unusually round (or less 'oblate') shape - because of the
disconnect between surface and core, the star is not spinning quite as much as
may appear just by looking at it from the outside." says
Byrne.

It's
not clear what's causing this disconnect between the surface and core spin
rates, but the researchers suggest that the presence of a magnetic field a
low latitudes around the star could be the culprit.

"Other
than a magnetic field, there are few alternative explanations for the reduced
oblateness," the researchers
conclude. "At this level of precision, the physics of stellar
oscillations may need to be studied in more detail."

The
team plans on using the technique on other stars in the future, to see how
rotations and magnetic fields can influence their shapes.